Prototyping a new wheel fitment calculator

[Oh Damn, it's Sam]

Hey all.

I am currently prototyping a new wheel fitment calculator and would appreciate any feedback before I move to the next stage in the process. Why yet another fitment calculator? The key distinction here is that mine takes camber into account, which is something I've not seen any other calculator able to do. It requires a couple additional measurements to work properly, but for people who want to change camber as part of their wheel fitment process, I think it will be helpful.

Like most fitment calculators, I provide a graphical display and give the change in position for both the outer and inner extremities of the tire, as well as the wheel lip and barrel. The interface looks as so:


The prototype spreadsheet is available here, and requires iWork '13. For those of you who do not have iWork, fear not, for dependent upon how much of a lazy shit I am, I am investigating developing versions for mobile or a Python version with a simple GUI for the desktop.

Any and all suggestions / complaints / feature requests / corrections to my math are appreciated. Let me know how it works for you.

[staystetti]

That's pretty neat, man. I would try to add an adjustable 'fender' line so users can tell how they'd fit.

[Robitussin]

That's pretty neat, man. I would try to add an adjustable 'fender' line so users can tell how they'd fit.

Yeah maybe a strut or coil line also.

[Oh Damn, it's Sam]

Thanks for the feedback, guys.

I'm looking into a way to add a fender line and a strut in the diagram, but since each car is unique, this feature would require a fair number of user-entered parameters. The concern I have is that by the time you've got enough data to be reasonably accurate, you're asking a lot from the user, which is liable to be confusing and create opportunities for mistakes. The strut in particular is challenging, since it needs to be located on the X/Y plane, set at an angle, given a major and minor diameter, and have the spring's upper and lower perch located along the axis of the strut. Even with all that, the model fails to work for suspension systems where the wheel's camber changes as the suspension cycles but the shock's does not or changes at a different magnitude.

The fender line is its own issue, since again, every car is unique. A simple two-point line is the obvious solution, but it fails to account for cars with complex fender geometry (such as cars with rounded fender flares). At a certain point, you're essentially creating a cross-sectional model of the fender just to see whether the wheel or tire fouls, which is not an awesome experience, and is a task that might be better left to getting under the car with a tape measure and a carpenter's square.

So, it's something I'm investigating, but as of yet, I don't have a good way figured out.

[baggedb16sentra]

I like this more then what's available. Have you thought of just doing basic drops and the user would have to figure out the rest themselves, in regards to camber and such?

[staystetti]

I mean a measurement of fender gap isn't that hard to input, they say they have 2.5" gap from wheel to fender and that tells you where the fender line is.

[Oh Damn, it's Sam]

I like this more then what's available. Have you thought of just doing basic drops and the user would have to figure out the rest themselves, in regards to camber and such?

Suspension height adjustment is something I can add if I come up with an acceptable way to put an adequate fender line / strut outline in the diagram. The user will, however, have to keep in mind whether their camber changes and whether the wheel moves inboard or outboard as the suspension cycles. For people who are after extremely tight fitment, this is where things get complicated.

I do want to keep the camber calculation in there, since that is the key feature that separates my calculator from the dozens of others on the market.

I mean a measurement of fender gap isn't that hard to input, they say they have 2.5" gap from wheel to fender and that tells you where the fender line is.

You're assuming the fender line is vertical, which is not necessarily the case.